
5 DUT Board Performance Considerations DUT Board Design for Mixed-Signal Tests
126 System Reference, January 2001
Grounding and Signal Shielding
Grounding Proper grounding is essential for precise measurements.
Mixed-signal devices differentiate between digital and
analog ground and often also between digital and analog
supply voltage.
You will need two ground planes on the DUT board which
are connected somewhere via an inductor as shown in the
following figure:
Figure 49 Digital Ground and Analog Ground
Shielding the Signals The safest way to transport signals between analog
modules and the DUT is via coaxial cables. The typical
impedance is 50 Ω (except for video signals, which usually
use 75 Ω).
The shields of digital signal cables must be connected to
digital ground, and the shields of analog signal cables to
analog ground.
AIN
AGND
VREF
D7
D5
D6
D4
D2
D3
D1
VDD
VCC
VSS
BUSY
RD
CS
NC
DGND
CLKIN
D0
DUT
Analog Ground
(Ground Plane)
Digital Ground
(Ground Plane)
DPS1
G1
GS1
P1
PS1
DPS2
G2
GS2
P2
PS2
DPS3
G3
GS3
P3
PS3
Digital
Channels
Digital
Channels
AWG
DPS4
G4
GS4
P4
PS4
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